ALBANY, N.Y. (AP) — Warmer weather in early spring is spawning more generations of some butterflies in northern climes and scientists are unsure if it will help or hurt the population in the long run.
The federally endangered Karner blue butterfly produced an unprecedented third generation this year in the Albany Pine Bush Preserve, said Neil Gifford, conservation director of the 3,200-acre pine barrens west of New York's capital.
The small, blue butterfly typically has two broods per year starting in late May or early June. But this year, the first butterflies were seen May 4, three weeks earlier than average, allowing time for a second brood in early July and a third in early August.
"The third flight is most likely the result of the record-setting early start to the 2012 Karner season," said Gifford, who's been leading recovery efforts for the rare species in the preserve for more than 16 years.
Karner blue butterfly managers from Wisconsin to New Hampshire have suspected since 2010 that the late-season adults they were seeing could represent a third brood, Gifford said.
"We don't yet have a good understanding of what the implications of a third brood will mean for the recovery of the species," Gifford said. "It will likely depend on whether the changing climate brings such conditions more frequently."
This is the hottest year on record so far for the Northeast, according to the Northeast Regional Climate Center at Cornell University. The Albany area had its warmest March on record this year with an average temperature of 45.9 degrees, a degree and a half above normal. The temperature hit the 90s for several days in April.
The Karner blue lives on spring-blooming lupines. The impact of the third brood on the insect's population depends on whether there are enough lupines left to feed the caterpillars.
Entomologist Tim McCabe at the State Museum says some other moths and butterflies are affected by warming springs. Canadian tiger swallowtails, giant swallowtails, and luna moths have produced additional broods in the past few years.
"Only in the last couple of years have I ever witnessed a second brood of luna moths," McCabe said. "In Florida, they typically have three broods a year and down around Pennsylvania and Virginia they have two, but in New York they usually have only one."
A Canadian variety of the tiger swallowtail butterfly that has always been a single-brood species is now having a significant second brood in New York, McCabe said. The same is true for the giant swallowtail, he said.
The fate of the third generation of Karner blues is uncertain because the caterpillars feed only on lupine plants, and with the hot, dry summer, the spring-blooming plants have been shriveling up. But if there's enough rain to keep the lupines around, it could mean a big boost for the population next spring, McCabe said.
Caterpillars from the second brood typically overwinter as pupae and hatch into butterflies in the spring. If all of the second brood emerged to produce the third brood this summer, and there aren't any lupines for the third brood to eat, that could leave none to overwinter and hatch to produce next spring's first brood.
But McCabe said it's possible that half the second brood has remained dormant to await spring, and in that case, there will be butterflies next spring regardless of whether the third generation survives.